1. Technical Field
The present invention relates generally to fiber optics based optical sensing, and more particularly to the use of such in analyzing stresses in structures and detecting defects there in.
2. Background Art
Fiber optics based optical sensing, signal processing, and components have a broad range of applications. Although probably best know in recent times for applications in communications and the boom in 1998–2001 in that industry, inventions applying fiber optics in other areas continue to be developed and can now particularly apply the infrastructure that the communications industry has provided. Many ideas that might have once seemed unduly academic to be put into practice can now be realized. As the present inventors have worked fiber communications systems, they have also adapted the underlying principles and crafted technology to use fiber optics for structure analysis and defect detection.
Structure defects have major significance for reliability and safety. Imagine if the fatigue of the craft used for China Airlines flight Cl 611 had been detected prior to take-off. The tragedy in which that craft broke apart in mid-air and 225 people perished might then have been averted. Modern “bullet” trains require track that must not shift appreciably, and in which even as little as one-millimeter of thermally induced expansion or contraction can be a serious safety concern. Ships and boats have similar concerns, as well as some additional ones. Submarines are subject to high pressures and strains, yet shipbuilders and failure analysis experts often have little more than engineering theory to guide them. But what to do in surface vessels after explosions, collisions, and battering in sever weather is not usually clear until an inspection can be completed, subjecting crew to risk and taking up precious time that may put the vessel in even further peril. If the two towers of World Trade Center had been equipped with a structure analysis system, the failure mode might have been recorded before the collapse and future so that architects and structural engineers could apply that data to design better buildings. Bridges and particularly dams are other examples of stationary structures where on-going structural analysis would produce immediate practical and long term academic benefits.
In sum, the need for better systems for defect detection and stress analysis in structures is enormous.